Walmart, the world’s No. 1 retailer and the nation’s largest seller of firearms, has cut ties with ALEC, the conservative nonprofit that has come under fire for promoting “Stand Your Ground” laws.

The Bentonville, Ark.-based company said Wednesday that it had suspended its membership with the American Legislative Exchange Council, joining nearly 20 other firms that have abandoned the controversial group after Florida’s Stand Your Ground law was initially cited as a reason not to indict a man in the killing of unarmed teenager Trayvon Martin there.

“Previously, we expressed our concerns about ALEC’s decision to weigh in on issues that stray from its core mission ‘to advance the Jeffersonian principles of free markets,’” Maggie Sans, Walmart vice president of public affairs and government relations, said in a May 30 letter addressed to ALEC’s national chairman and executive director. “We feel that the divide between these activities and our purpose as a business has become too wide.”

The company has been a member of ALEC since 1993. Sans has served as the secretary of ALEC’s 21-corporation private enterprise for the past year.

The loss of such a prominent member could be disastrous for the organization, which is also trying to fend off accusations that it is illegally lobbying state lawmakers. The group, which is organized under tax code 501(c)(3) and is barred from political activity including lobbying, brings corporations and lawmakers together to craft and promote legislation. The Minnesota Campaign Finance and Public Disclosure Board said earlier this week that it will investigate complaints filed by Common Cause.

Liberal activists — led by African-American advocacy group Color of Change — have successfully pressured nearly 20 consumer-facing firms to drop their ALEC memberships. Just last week Amazon joined the list of high profile defectors that includes Yum Brands Inc., Blue Cross Blue Shield and Procter &amp; Gamble Co.

But Walmart’s announcement was a particularly significant win because of its size and its efforts to court the black community.

The activists, in partnership with another group called Making Change at Walmart, have targeted the company with rallies, emails and phone calls for months. The pressure escalated in the wake of reports that Walmart bribed Mexican officials as it expanded south of the border.

The activists argued that the company’s support of ALEC was yet another example of insensitivity to the African-American and Latino communities. In recent years, Walmart has worked to court Democrats, particularly those with ties to the Congressional Black Caucus and the Congressional Hispanic Caucus.

“They are supporting civil rights causes on one hand and anti-civil rights causes on the other,” the Rev. Jesse Jackson told Roll Call in April. “The Trayvon Martin case has exposed their duplicity.”

The activists allege that Walmart, the largest firearms retailer in the United States, could benefit from gun-friendly laws such as the Florida statute at the center of the Trayvon Martin murder case.

Walmart executive Janet Scott served as the co-chairwoman of ALEC’s Criminal Justice Task Force in 2005, according to an ALEC spokesman, when the panel approved the model language for Stand Your Ground laws.

ALEC, which was quiet at first, announced in April that it would disband that task force, which also promoted voter identification measures that have passed in at least half a dozen states.

“We’re always sad to see any member — including Wal-Mart — leave, but on balance our membership across the board has grown over the past year,” said ALEC spokesman Kaitlyn Buss in an email. “While we are disappointed in Wal-Mart’s decision, we understand the unique pressures they are under. However, as we announced in April, ALEC is solely focused on limited government, free-market solutions in the states that create jobs and improve the economy.”